To date, in a wireless communication system having a base station and a plurality of wireless communication terminals, each wireless communication terminal transmits a plurality of packets to the base station. Typically, each wireless communication terminal transmits packets at times determined by the wireless communication terminal. A plurality of packets from different transmission sources sometimes collide with each other in a period during which packet transmissions from wireless communication terminals contend with each other (hereinafter referred to as a “contention period”). A packet collision in the contention period blocks arrival of the packets at the base station. As a result, in this case, the base station requests each wireless communication terminal to retransmit a packet that has not arrived. In order to avoid such a collision, the base station sets, for a particular wireless communication terminal, a period during which packet transmissions will not contend with each other (hereinafter referred to as a “contention-free period”), and the particular wireless communication terminal transmits a packet addressed to the base station in the contention-free period.
Japanese Laid-open Patent Publication No. 2007-67654 is an example of the related art.